Chronic wounds affect three million people each year in the U.S. Chronic wounds generally involve any break, or ulceration, of the skin that is of long duration or recurs frequently. Such wounds cause pain, loss of function, force changes in an individual's life through potential lack of mobility, take extended periods of time for recovery, and require high amounts of patient compliance for recovery.
Chronic wounds disrupt the integrity of the skin by tearing, cutting, piercing or breaking the tissue. The causes may be structural, such as injury, or physiological, such as an underlying disease. The most frequently occurring skin wounds are venous ulcers, pressure ulcers and diabetic foot ulcers.
Chronic wounds are a serious health concern with substantial morbidity. They also are a source of frustration to both physician and patient, as lengthy treatments, treatment failures and the need for long periods of patient compliance prove challenging. The wounds take so long to heal that compliance drops off and worsens when reversals occur or new ulcers appear.
Chronic wounds occur in individuals with underlying diseases of various types whose medical conditions compromise the body's ability to repair injured tissue on its own. Despite the use of a variety of medical and surgical treatments, chronic wounds can take months or even years to heal and frequently recur. These wounds are often large and unsightly and may be painful in some patients.
Chronic wounds are of three major types: venous stasis ulcers, diabetic ulcers and pressure ulcers. A venous ulcer is an ulceration that develops on the ankle or lower leg in patients with chronic vascular disease. In these patients, blood flow in the lower extremities is impaired, leading to edema (swelling) and mild redness and scaling of the skin that gradually progress to ulceration. Venous ulcers are a condition affecting 500,000-700,000 patients in the US and 1.3 million people in the industrialized world.
A diabetic ulcer is a chronic wound that occurs in patients with diabetes. While the actual cause of the ulcer in these patients is an injury such as a callus, blister or foreign body such as a pebble or splinter, it is the patient's underlying disease that places him or her at high risk for developing an ulcer. Important risk factors include: inadequate local blood supply, which impairs their ability to repair injured tissue and ward off infection, and reduced sensation in the extremities, which causes the initial injury to go unrecognized until it becomes a serious, chronic wound. Diabetic ulcers are a condition affecting just under 500,000 patients in the US and 1.2 million people in the industrialized world.
A pressure ulcer is defined as any lesion caused by unrelieved pressure on tissues that are located over a bony prominence on the body. Pressure ulcers were formerly referred to as bedsores or decubitus ulcers. Pressure ulcers develop in immobile patients whose tissues are subjected to continuous pressure from bones on the interior and hard surfaces such as beds or chairs on the exterior. In addition to their immobility, patients at risk for the development of pressure ulcers typically have poor nutritional status, inadequate hydration, and other underlying medical conditions that compromise their ability to heal injuries. Pressure ulcers affect over 1.6 million people in the US and 4.1 million people in the industrialized world. Estimates of the prevalence of these conditions vary greatly. Estimates as high as 12 million patients have been reported for all types of chronic wounds in the industrialized markets.
Chronic wounds can be of variable sizes and depths. In general, there are four layers of tissue that can potentially sustain injury in a wound, the epidermis, or outermost layer; the dermis; the subcutaneous tissue; and, at the deepest layer, muscle, tendon, and bone. Partial-thickness ulcers involve a loss of skin that is limited to the epidermis and, potentially, part of the dermis. These wounds heal by epithelialization (proliferation and migration of epithelial cells). Full-thickness ulcers involve damage or necrosis of the epidermis, dermis, and subcutaneous tissue, and may extend into the connective tissue below the dermis. These wounds heal by granulation (filling of the wound with connective tissue), contraction, and epithelialization. The most severe category of ulcer involves injury to the epidermis, dermis, subcutaneous tissue, and muscle, tendon, or bone. The wound healing process is not complete even after the wound has closed. The process of rebuilding normal skin and tissue in a wound can take up to two years after the initial injury.
Treatment of chronic wounds varies with the severity of the wound. Partial- and full-thickness wounds are typically treated with dressings and debridement (use of chemicals or surgery to clear away necrotic, or dead, tissue). Antibiotics may be used in the event of an infection. Partial-thickness to full-thickness wounds represent the largest categories of chronic wound patients, the areas of greatest unmet medical need, and the categories most amenable to treatment with prescription growth factor therapy such as Repifermin. Patients with full-thickness wounds extending into muscle, tendon or bone are at significant risk of sepsis and are typically treated with surgery.
Despite the number of conservative therapies available, chronic wounds remain a very frustrating problem for health care practitioners because of the time-consuming nature of treatment regimens and patient non-compliance. What is needed is a therapy that can increase a practitioner's success in healing chronic wounds and/or accelerate the rate of chronic wound healing.